I previously wrote about my fruitless search to find the file format of iTunes Music Library files, and how I was able to use the iTunes COM Windows SDK to bypass this lack of knowledge.
If you do a search on Google for "hdfm itunes", my COM story is the first result. The third result, however, is Perl programmer Brian D. Foy's Mac-iTunes Perl module, which includes a description of the iTunes Music Library file format. This is annoying, since I was looking for this information back in early June, and could not find it. The page was written in 2002, but did not appear in any of the multiple Google searches I did.